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The Single UNIX &reg; Specification, Version 2<br>
Copyright &copy; 1997 The Open Group

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<h4><a name = "tag_000_001_167">&nbsp;</a>NAME</h4><blockquote>
alarm - schedule an alarm signal
</blockquote><h4><a name = "tag_000_001_168">&nbsp;</a>SYNOPSIS</h4><blockquote>
<pre><code>

#include &lt;<a href="unistd.h.html">unistd.h</a>&gt;

unsigned int alarm(unsigned int <i>seconds</i>);
</code>
</pre>
</blockquote><h4><a name = "tag_000_001_169">&nbsp;</a>DESCRIPTION</h4><blockquote>
The
<i>alarm()</i>
function causes the system to generate a SIGALRM signal for the 
process after the number of real-time seconds specified by
<i>seconds</i>
have elapsed.
Processor scheduling delays may prevent the process from handling the
signal as soon as it is generated.
<p>
If
<i>seconds</i>
is 0, a pending alarm request, if any, is cancelled.
<p>
Alarm requests are not stacked; only one SIGALRM generation can be
scheduled in this manner; if the SIGALRM signal has not yet been
generated, the call will result in rescheduling the time at which
the SIGALRM signal will be generated.
<p>
Interactions between
<i>alarm()</i>
and any of
<i><a href="setitimer.html">setitimer()</a></i>,
<i><a href="ualarm.html">ualarm()</a></i>
or
<i><a href="usleep.html">usleep()</a></i>
are unspecified.
</blockquote><h4><a name = "tag_000_001_170">&nbsp;</a>RETURN VALUE</h4><blockquote>
If there is a previous
<i>alarm()</i>
request with time remaining,
<i>alarm()</i>
returns a non-zero value that is the number of seconds
until the previous request would have generated a SIGALRM signal.
Otherwise,
<i>alarm()</i>
returns 0.
</blockquote><h4><a name = "tag_000_001_171">&nbsp;</a>ERRORS</h4><blockquote>
The
<i>alarm()</i>
function is always successful, and no return value is reserved to
indicate an error.
</blockquote><h4><a name = "tag_000_001_172">&nbsp;</a>EXAMPLES</h4><blockquote>
None.
</blockquote><h4><a name = "tag_000_001_173">&nbsp;</a>APPLICATION USAGE</h4><blockquote>
The
<i><a href="fork.html">fork()</a></i>
function clears pending alarms in the child process.
A new process image created by one of the
<i>exec</i>
functions inherits the time left to an alarm signal in the old
process' image.
</blockquote><h4><a name = "tag_000_001_174">&nbsp;</a>FUTURE DIRECTIONS</h4><blockquote>
None.
</blockquote><h4><a name = "tag_000_001_175">&nbsp;</a>SEE ALSO</h4><blockquote>
<i><a href="exec.html">exec</a></i>,
<i><a href="fork.html">fork()</a></i>,
<i><a href="getitimer.html">getitimer()</a></i>,
<i><a href="pause.html">pause()</a></i>,
<i><a href="sigaction.html">sigaction()</a></i>,
<i><a href="ualarm.html">ualarm()</a></i>,
<i><a href="usleep.html">usleep()</a></i>,
<i><a href="signal.h.html">&lt;signal.h&gt;</a></i>,
<i><a href="unistd.h.html">&lt;unistd.h&gt;</a></i>.
</blockquote><h4>DERIVATION</h4><blockquote>
Derived from Issue 1 of the SVID.
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UNIX &reg; is a registered Trademark of The Open Group.<br>
Copyright &copy; 1997 The Open Group
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